asyncio简单入门（二）

电玩女神 2022-05-13 23:22 162阅读 0赞

## 请求网页 ##

**方法一：**

import asyncio
    import requests
    
    
    async def main():
        loop = asyncio.get_event_loop()
        future1 = loop.run_in_executor(None, requests.get, 'http://www.baidu.com')
        future2 = loop.run_in_executor(None, requests.get, 'http://www.python.org')
        response1 = await future1
        response2 = await future2
        print(response1.text)
        print(response2.text)
    
    loop = asyncio.get_event_loop()
    loop.run_until_complete(main())

**方法二：**

> copy from liaoxuefeng  
> [https://www.liaoxuefeng.com/wiki/0014316089557264a6b348958f449949df42a6d3a2e542c000/001432090954004980bd351f2cd4cc18c9e6c06d855c498000][https_www.liaoxuefeng.com_wiki_0014316089557264a6b348958f449949df42a6d3a2e542c000_001432090954004980bd351f2cd4cc18c9e6c06d855c498000]

import asyncio
    
    @asyncio.coroutine
    def wget(host):
        print('wget %s...' % host)
        connect = asyncio.open_connection(host, 80)
        reader, writer = yield from connect
        header = 'GET / HTTP/1.0\r\nHost: %s\r\n\r\n' % host
        writer.write(header.encode('utf-8'))
        yield from writer.drain()
        while True:
            line = yield from reader.readline()
            if line == b'\r\n':
                break
            print('%s header > %s' % (host, line.decode('utf-8').rstrip()))
        # Ignore the body, close the socket
        writer.close()
    
    loop = asyncio.get_event_loop()
    tasks = [wget(host) for host in ['www.sina.com.cn', 'www.sohu.com', 'www.163.com']]
    loop.run_until_complete(asyncio.wait(tasks))
    loop.close()

**方法三：**

> 在一个web上，一个工程师做了一个探索。发现，当使用aiohtt+asyncio时候是比requests要快很多倍的。所以，推荐使用原装的库。

import aiohttp
    import asyncio
    
    async def fetch(session, url):
        async with session.get(url) as response:
            return await response.text()
    
    async def main():
        async with aiohttp.ClientSession() as session:
            html = await fetch(session, 'http://python.org')
            print(html)
    
    loop = asyncio.get_event_loop()
    loop.run_until_complete(main())

## aiohttp简单测试 ##

import aiohttp
    import asyncio
    import time
    import requests
    
    
    async def fetch(session, url):
        async with session.get(url) as response:
            return await response.text()
    
    
    async def main():
        async with aiohttp.ClientSession() as session:
            await fetch(session, 'http://python.org')
    
    
    st = time.time()
    loop = asyncio.get_event_loop()
    loop.run_until_complete(main())
    et = time.time()
    print(et - st)
    
    st = time.time()
    res_text = requests.get('http://python.org').text
    et = time.time()
    print(et - st)

输出结果是：

3.109215259552002
    2.7337353229522705

目前来看，只爬一个页面的话，其实反而request会快点。

但是当爬取的数目提高的时候就发送了变化了。

import aiohttp
    import asyncio
    import time
    import requests
    
    
    async def fetch(session, url):
        async with session.get(url) as response:
            return await response.text()
    
    
    async def main():
        async with aiohttp.ClientSession() as session:
            await fetch(session, 'http://python.org')
    
    
    st = time.time()
    loop = asyncio.get_event_loop()
    loop.run_until_complete(asyncio.wait([main(), main()]))
    et = time.time()
    print(et - st)
    
    st = time.time()
    res_text = requests.get('http://python.org').text
    res_text_2 = requests.get('http://python.org').text
    et = time.time()
    print(et - st)

输出：

3.1400091648101807
    5.478497505187988

当然啦，这是因为第一个其实是采用是协程技术，所以，差别有点大也是可以理解的。

所以，我们要接着探究。

## 对比 gevent和aiohttp ##

这个非常有意思，因为两者都是关于协程的，关于随者更优对比一下就可以知道结果了。

**文件结构：**  
三个文件放在同一个目录下：

*  main\_Test.py
 *  asyncio\_Test.py
 *  gevent\_Test.py

**main\_Test.py**

import asyncio_Test
    import gevent_Test
    import matplotlib.pyplot as plt
    
    asyncio_list = []
    gevent_list = []
    
    N = 50
    Begin = 1
    url = 'http://www.python.org'
    for i in range(N):
        asyncio_list.append(asyncio_Test.f(Begin + i, url))
        gevent_list.append(gevent_Test.f(Begin + i, url))
    
    plt.plot(asyncio_list, label='asyncio')
    plt.plot(gevent_list, label='gevent')
    
    plt.legend()
    plt.savefig('1.png')
    plt.show()

**asyncio\_Test.py**

import aiohttp
    import asyncio
    import time
    
    
    async def fetch(session, url):
        async with session.get(url) as response:
            return await response.text()
    
    
    async def main(Target_url):
        async with aiohttp.ClientSession() as session:
            await fetch(session, Target_url)
    
    
    def f(Times, Target_url):
        st = time.time()
        loop = asyncio.get_event_loop()
        task = [main(Target_url)] * Times
        loop.run_until_complete(asyncio.wait(task))
        et = time.time()
        return et - st

**gevent\_Test.py**

import gevent
    from gevent import monkey
    import time
    import requests
    monkey.patch_socket()
    
    
    def request_f(Target_url):
        res_text = requests.get(Target_url).text
    
    
    def f(Times, Target_url):
        st = time.time()
        WaitList = [gevent.spawn(request_f, Target_url)] * Times
        gevent.joinall(WaitList)
        et = time.time()
        return et - st

对比效果如下：

![这里写图片描述][70]

可以发现，当只爬取一个网页的时候，其实，反而用gevent+request会更快。  
随着每次爬取的网页是数目的累积，只有当爬取的数目接近20个的时候，asyncio才普遍低于gevent（虽然也是基本接近）。

相差只有0.01秒左右（我直接把数值输出来过）

## 会接着更新这个。。 ##

[https_www.liaoxuefeng.com_wiki_0014316089557264a6b348958f449949df42a6d3a2e542c000_001432090954004980bd351f2cd4cc18c9e6c06d855c498000]: https://www.liaoxuefeng.com/wiki/0014316089557264a6b348958f449949df42a6d3a2e542c000/001432090954004980bd351f2cd4cc18c9e6c06d855c498000
[70]: /images/20220514/a99f773d67474a65b2dd8d5c0b29d7ca.png